U.N. set to extend inquiry into Syria toxic gas attacks: diplomats

UNITED NATIONS, Nov 17 (Reuters) - The U.N. Security Council was set to approve on Thursday a one-year extension of an international inquiry charged with laying blame for chemical weapons attacks in Syria, diplomats said, paving the way for a showdown over how to punish those responsible.

Russia has said it wants the inquiry to be broadened to look more at the "terrorist chemical threat" within the region and the draft resolution to renew the mandate includes language to reflect that request, diplomats said.

The inquiry by the United Nations and the Organization for the Prohibition of Chemical Weapons (OPCW), set up by the council a year ago, has already found that Syrian government forces were responsible for three chlorine gas attacks and that Islamic State militants had used mustard gas.

Syria's government has denied its forces had used chemical weapons during the country's nearly six-year-old civil war.

France, Britain, the United States and other council members have said that after the renewal of the inquiry on Thursday, they hope to start negotiations on a draft resolution to punish those blamed for the attacks, likely with U.N. sanctions.

However Russia, an ally of Syria's President Bashar al-Assad, has said the inquiry's findings cannot be used to take action at the U.N. Security Council and that the Syrian government should investigate the accusations.

Last week the OCPW's executive body voted to condemn the use of banned toxic agents by the Syrian government and Islamic State militants.

Chlorine's use as a weapon is prohibited under the Chemical Weapons Convention, which Syria joined in 2013. If inhaled, chlorine gas turns to hydrochloric acid in the lungs and can kill by burning lungs and drowning victims in the resulting body fluids.

Syria agreed to destroy its chemical weapons in 2013 under a deal brokered by Moscow and Washington. The Security Council backed that deal with a resolution that said in the event of non-compliance, "including unauthorized transfer of chemical weapons, or any use of chemical weapons by anyone" in Syria, it would impose measures under Chapter 7 of the U.N. Charter.

Chapter 7 deals with sanctions and authorization of military force by the Security Council. The body would need to adopt another resolution to impose targeted sanctions - a travel ban and asset freeze - on people or entities linked to the attacks. (Editing by James Dalgleish)